Generally, a prior art air conditioner uses a large scale refrigerating device to offer enough cool air for each floor of a building. The large scale of a refrigerating device is needed to use cool water so as to keep the temperature of the refrigerating device in lower temperatures with preferred heat exchange effect by use of the cooling water recycling in the refrigerating device and further prevent from tripping of the refrigerating device. However, cooling water of a prior art of an air conditioner is usually pumped from the refrigerating device and stays in a water storage tank for cooling down, and then is injected again into the refrigerating device so as to offer the recycling cooling water repeatedly. After the cooling water of the prior art is recycled in the refrigerating device, the cooling water stays in water storage tank for cooling down and flows immediately into the refrigerating device again without any filtering and sterilizing process. The wall of the water storage tank for cooling water is easy to be adhered by bacteria and algae after a period time using, which is easy to cause related diseases. For instance, Legionellosis is caused by polluted air environment. Bacteria is contained in the recycling cooling water of the prior art and algae is adhered to the wall of the water storage tank, which cause problems of a condenser having limescale and being corroded. Although the water storage tank may be cleaned, the cleaning process is simple by use that the cooling water is drained out and then refilled new cooling water. Otherwise, the water storage tank is cleaned only partially in visible areas. The other invisible areas in the inside of the water storage tank are not only difficult to be cleaned and usually ignored, but also easy to offer good breeding environment for bacteria. The water storage tank is difficult to be cleaned completely and is contained with bacteria, which is the weakness of the air conditioner of the prior art.
The problems caused by the cooling water, such as corrosion, limescale and bacteria in the water storage tank, has been encountered, when more and more new modern buildings, such as a hospital, an office, a restaurant and a department store, are constructed recently. However, the problems are unable to be solved by use of adding drug of the prior art. On the contrary, the prior art method of adding drug causes more serious environmental pollution problem.